The present invention relates to cutting of materials and, in particular, it concerns a method and device employing microwave radiation to cut into non-conductive materials.
One of the most fundamental and most frequently performed mechanical operations is the drilling of holes. Of particular relevance here is the drilling of holes in hard non-conductive materials such as stones, rocks, marble, silicates, ceramics, concrete, brick etc. which is required in a wide range of applications including almost all machining and construction work.
Drilling of holes in such materials is typically performed by use of mechanical drills. The operation of mechanical drills is very noisy and generates large amounts of dust which may be damaging to equipment and harmful to people and the environment. Generation of dust also requires costly cleaning.
There exist laser-based cutting systems in which a laser is used to drill holes in various materials. An example of such a system is described in A. C. Metaxas, "Foundations of Electroheat", John Wiley and Sons, 1996. These lasers operate mainly in the infrared range (primarily CO.sub.2 lasers at 10.6 .mu.m wavelength). Laser based systems provide a non-mechanical alternative for making small accurate holes. However, these devices are relatively expensive and are not suitable for general purpose use.
In the field of microwave engineering, devices have been proposed for a wide range of manufacturing and treating processes. These include consolidation of materials, sintering of ferrites and ceramics, dewaxing of casting molds, fast setting of concrete and asphalt, and gluing processes. Most of these applications are implemented inside special microwave furnaces or applicators.
It has also been known for several years that thermal fluctuations caused by high-power microwaves may be used to fracture rocks and concrete. Examples of such applications are described in U.S. Pat. Nos. 5,003,144 to Lindroth et al. and 5,635,143 to White et. al. However, microwaves do not seem to have been used directly for drilling holes in a solid body.
It is also known that an open-ended coaxial applicator may be used for joining of ceramic sheets. Such a device is described by Tinga et al., "Open Coaxial Microwave Spot Joining Applicator", Ceramic Transactions 1995, Vol. 59, pp. 347-355. The applicator described therein may be effective to cause a localized hot spot which can be used to join elements. However, the end of the suggested applicator structure is covered by a dielectric plate, rendering it incapable of drilling or cutting into the material.
There is therefore a need for a method and device employing microwave radiation to drill into or otherwise cut non-conductive materials.